This invention relates to a shift lever device for use with a bicycle, and more particularly to a gear shift lever device for shifting a bicycle drive chain from one size sprocket to another size one in cooperation with a rear derailleur.
In a bicycle equipped with a multiple freewheel having a plurality of different size sprockets and a rear derailleur, the chain shifting is generally performed by pulling or releasing a tensioned flexible cable which is operatively connected at one end to the shift lever device mounted on a handlebar or the like and at the other end to the rear derailleur supported by a certain portion of a bicycle frame adjacent to the freewheel. As is well known in the art, the gear shift lever device is basically different from a brake lever device in such a point that the latter has an automatic return system for releasing and thus requires only oneway positive manipulation for braking, whereas the former must be positively manipulated pivotally in opposite directions by overcoming a certain amount of friction and tension force imposed thereon. Thus, in operation, a cyclist must remove his hand from the handlebar, which is likely to cause less safety and control of the bicycle.
The general idea of designing the shift lever so as to permit manipulation without a cyclist's removing his hand from a handlebar has been proposed, for instance, in U.S. Pat. No. 3,742,777 to Mathauser and also in U.S. Pat. No. 3,972,247 to Armstrong. According to Mathauser, a hydraulically operated mechanism with a pivotal lever is employed, while according to Armstrong, a ratchet mechanism with a pivotal lever is employed. According to the present invention, however, a slide shaft mechanism with a push-button is employed for easier manipulation and simpler construction.
Therefore, an object of the present invention is to provide an improved shift lever device of novel construction which can be mounted on a bicycle handlebar so that a cyclist can manipulate it without removing his hand from the handlebar.
Another object of the invention is to provide an improved shift lever device which is relatively simple and compact in construction, easy to manipulate, efficicent in use and inexpensive to manufacture.
A further object of the invention is to provide an improved shift lever device which is provided with a slide shaft and push-button system.
Still a further object of the invention is to provide an improved shift lever device which facilitates shifting the gears in one way by a single stroke of a lever and in the other way in a step-by-step fashion by operation of a push-button.
Other objects, features and advantages of the present invention will become more apparent from the following detailed description taken in connection with the accompanying drawings; it should be understood, however, that the detailed description and specific example, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description.